REU: Supplement - Development of Signaler and Receiver Phenotypes

Differences among individual in performance, such as in the level of reproductive output, the quality of phenotype, or the ability to withstand stress, exist in almost any population examined. For example, males of many animals differ in behavior and appearance in ways that lead to differences in mating success (Andersson 1994). How they come to be so different is a major focus of research given that females may benefit from mating with certain males (e.g., Kirkpatrick & Ryan 1992). Females also vary substantially in performance. In birds, individual females differ in when they begin breeding (e.g., Brommer et al. 2005, Nussey et al. 2005), how many eggs they lay (e.g., Sheldon et al. 2003), the size of those eggs (e.g., Hipfner et al. 2005), and in their batching success (e.g., Cordero et al. 2004, Komdeur et at. 2005). Such differences in performance have considerable effects on a variety of behavioral traits (e.g., producer- scrounger strategies, Barnard & Sibly 1981). That such differences persist is also puzzling given that they would seem to be under strong selection. While interest is growing in possible genetic bases for performance differences (e.g., Sheldon et al 2003, Brommer et at. 2005, Nussey et al. 2005), very little attention has been given to the potential influence of developmental processes. Wheelwright & Templeton (2003) tested the development of foraging skills in juvenile Savannah sparrows (Passerculus sandwichensis) and found significant improvement at 22-24 days of age. This corresponds to the age at which parents cease providing care. However, this study did not address variation in skill development. Variation in early types of experience, either in task heterogeneity or in social context, could also lead to relatively fixed differences in adulthood and therefore variation in performance. The goal of this REU project is to collect data on the development of skills at foraging and achieving high rank in social interactions in a common passerine bird, the house sparrow (Passer domesticus). My lab is currently investigating, with funding from NSF, both the functional influences of male plumage characters on social interactions in house sparrows and also the developmental processes that produce a range of different plumage patterns. Here I propose that an REU intern engage in a parallel project describing the key events in the transition from dependent offspring to independent juvenile, and testing some of the potential factors influencing this shift. Specifically, the REU student wilt: * Document behavioral shifts from total dependence on a care-giver for food to feeding independently, * Evaluate methods for measuring skill sets associated with foraging (such as finding cryptic food or adapting to changing food types or cues to food), and * Test some initial hypotheses about the factors that might affect acquisition of those skill sets. The student will begin work in mid-Spring at our field population located just outside of Lexington, KY where they will gain training in general field methods such as checking nest boxes and observing free-living parents. Subject birds will be removed from the nest at 4-5 days of age and reared by hand, something we have done successfully several times in the past. The REU student will hand-rear nestlings to independence white collecting data on their skill acquisition. The student will record rates of nestling growth rate, feeding, and feather growth, and the age at which several developmental stages are reached (e.g., ability to track food with head, first movement toward food, first independent pecking, and first unassisted feeding). The student will also measure age-related performance on standardized foraging tasks, such as finding food buried in sand. Finally, if time permits we will carry out an experiment to test the effect of being housed socially on development of foraging skills